Apparatus for making letterpress plates

ABSTRACT

A hydraulic press supporting a lower press member including a center and end sections each having an internal passageway and with an engraved master plate mounted on the center section, an automatically controlled system for circulating cooling fluid through the passageways in the end sections and alternately circulating cooling and heating fluid through the passageway in the center section for preheating and cooling the plates, a thermoplastic sheet of material pressed against the preheated plate by an upper press member having a resilient blanket and held until the plate and sheet are cooled, and a frame slidably mounted on the lower press member for shifting the sheet a predetermined distance to form a flexible mat having a pair of identical impressions in precise registration for use in producing a two-on plate for a letterpress.

United States Patent [72] inventors Charles W. Bunting; 3,125,952 3/ l964 Bungay 101/401.1 David P. Groeber, Dayton; Louis W. Pettlo,3,193,599 7/1965 Crilly 18/22X Springboro, Ohio 3,359,600 12/1967 OBrienet al ...18/Preheat Digest [21 1 Appl. No. 663,858 960,006 l 910Droitcour 101/401.1UX [22] Filed Aug. 28, 1967 1,377,509 5/1921 Novotny101/401.1UX [45] Patented Mar. 9, 1971 2,364,597 12/1944 Atwood..... 18/17X [73] Assignee McCall Corporation 2,542,263 2/1951 Schultz 264/327New York, N.Y. 3,241,189 3/1966 Siempelkamp... 101/93(P)X 3,396,7838/1968 Siempelkamp 18/17(H)X 3,408,437 10/1968 Wheeler et a1 101/401 1 X[54] APPARATUS FORMAKING LETTERPRESS Primary Examiner-Robert E. PulfreyPLATES Assistant Examiner Eugene H Eickholt 6 Chums 10 Drawing Figs-Attorney-Marechal, Biebel, French and Bug [52] U.S.Cl l0l/401.l,

264/327, 100/93, 18/22 [51] f" n 1,10 ABSTRACT: A hydraulic presssupporting a lower press' [50] Fltld ofSearch 264/327; member includinga center d end Sections h h i an 101/401.1; 18/17 (H), 5.3 (H); 101/9,32; internal passageway and with an engraved master plate 100/93;156/583; 18/19(Part1al), 22, 23, 5 mounted on the center section, anautomatically controlled (lnquu'ed) system for circulating cooling fluidthrough the passageways in 56 R f Cited the end sections and alternatelycirculating cooling and heatl e ing fluid through the passageway in thecenter section for pre- UNITED STATES PATENTS heating and cooling theplates, a thermoplastic sheet of 2,491,027 12/1949 7 Belcher et all01/401.1 material pressed against the preheated plate by an upper press2,580,883 l/ 1952 Borklanclm, 18/ 19F member having aresilient blanketand held until the plate and 2,686,552 8/1954 Faeber et al.. 101/401.1UXsheet are cooled, and a frame slidably mounted on the lower 2,700,179l/195 5 Benson 18/190X press member for shifting the sheet apredetermined distance 2,722,038 1 1/ 1955 Freund 18/48 to form aflexible mat having a pair of identical impressions in 2,971,249 '2/1961 Anderson et al.. ...l 8/Stencil Digest precise registration for usein producing a two-on plate for a 3,031,959 5/1962 Libberton 101/401.1Xletterpress.

H5 55 6 z 90 85 ml\m 58 97 35 g m ,1 14 63 l j H GP 1 (I 52 E 46 49 ,-6039 4am l a 2 I v 5 r26 1 J, 68 Y l, 68 5 a 0 v i J Ii i l I 29 h -P, l29 s real 4s 49 M v 5.18 62 l 1 1 I-P W "A o l i 56".*"--' i 1 L- |I-- IHe 4 58 so 35' 4 Patented March 9, 1971 3 Sheets-Sheet 8 6 6 m m A 5 mTO DRAIN STEIWL STEAM REGULATOR RELAY v R APPARATUS FOR MAKINGLJE'ITERPRESS PLATES BACKGROUND OF THE INVENTION In the production ofpart-cylindrical plates for mounting on the rolls of a letterpress, aflexible matrix or mat is made by first preheating a flat originalengraved plate within a device commonly referred to as a clamshellhaving internal passageways through which a heating fluid such as steamis circulated. After preheating, the engraved plate is removed from theclamshell and a sheet of vinyl is placed on the mat with an overlay of aresilient blanket, and the sandwiched assembly of the plate, vinyl sheetand blanket is inserted within a hydraulic press where substantialpressure is applied to mold in the vinyl sheet an impression of theengraved plate. The sheet and the engraved plate are then cooled withinthe press while pressure is maintained to form a flexible vinyl mat. Oneor more metal layers are electrolytically deposited on the mat and thethin sheet of deposited metal is then separated from the vinyl sheet toform a flexible electrotype which is laminated to a precurvedreinforcing mat and this laminated assembly is trimmed to form theletterpress plate.

It has been found desirable to avoid the transfer operation of thepreheated engraved plate from the clamshell to the high pressure pressafter adding the vinyl sheet and blanket to increase efficiency inproducing a mat and to avoid heat loss from the plate during thetransfer. Furthermore, for efficiently printing some smaller books ormagazines, it is frequently desirable to form a mat having a pair ofidentical impressions in precise registration for producing a two-onletterpress plate on which two impressions are spaced circumferentiallyin relation to the roll of the letterpress on which the plate ismounted.

SUMMARY OF THE INVENTION The present invention is directed to animproved method and apparatus for efficiently producinga flexible vinylmat and which is especially suited for forming a two-on mat or a four-onmat having corresponding pairs of identical impressions all'in preciseregistration. Thus the method and apparatus of the invention provide forefficiently constructing either two-on or four-on letterpress plates andthereby substantially reduce the time required to mount and align a setof plates on the plate cylinders of the letterpress for a particularprinting job.

According to a preferred embodiment of the invention, a two-on mat isproduced by securing an engraved master plate to the center section of aflat lower press member which slidably supports a U-shaped frame towhich is secured a sheet of vinyl. Cooling fluid is circulated throughpassageways formed within each end section of the press member andcooling and heating fluid are alternately circulated through apassageway within the center section directly under the engraved plate.

The lower press member, master plate and the vinyl sheet are carriedinto a hydraulic press where a portion of the vinyl sheet is held inlight contact with the engraved face of the master plate by a resilientblanket mounted on an upper press member while the master plate andvinyl sheet are preheated by circulating steam through the centersection of the lower press member. After the master plate reaches apredetermined temperature, the sheet of vinyl is pressed against theengraved face of the plate by raising the lower press member toward theupper press member.

As the high pressure is being applied, cool water is circulated throughthe center section of the lower press member in place of thesteam tocool the corresponding portion of the vinyl sheet while the remainingportion of the vinyl sheet is maintained cool by the water beingcirculated through the adjacent end section of the lower press member.After one impression is made in the vinyl sheet, the sheet is shifted apredetermined distance by sliding the frame laterally and a secondimpression is formed within the vinyl sheet by repeating the aboveprocedure. As a result, two identical impressions can be quickly formedwithin the sheet with the impression BRIEF DESCRIPTION OF THE DRAWINGSFIG. I is a perspective view of apparatus for forming a flexible mat inaccordance with the invention;

FIG. 2 is a perspective view of a vinyl sheet and the upper and lowerpress members forming a part of the apparatus shown in FIG. 1;

FIG. 3 is a plan view of the lower press member with two engraved platesmounted thereon;

FIG. 4 is an elevation view of the upper and lower press members astaken generally on the line 4-4 of FIG. 3;

FIG. 5 is a section of the lower press member taken generally on theline 5-5 of FIG. 3;

FIG. 6 is a side elevational view of the upper press member and asection of the lower press member taken generally on the line 6-6 ofFIG. 3;

FIG. 7 is a schematic flow diagram showing the circulation of heatingand cooling fluid through the lower press;

FIG. 8 is a view of a typical mat formed in accordance with theinvention and having two sets of two-on impressions;

FIG. 9 is a fragmentary section of the lower press member as takengenerally on the line 5-9 of FIG. 5; and

FIG. 10 is an enlarged fragmentary section as taken on the line 1040 ofFIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 shows a hydraulic moldingpress 15 of the type manufactured by Ostrander-Seymour Company, MelrosePark, Illinois, and generally includes a base 16 which supports a table18 movable horizontally between an extended position (FIG. I) and aretracted position (not shown) under a head portion 20 where the tableis moved vertically by a hydraulic cylinder (not shown) mounted on thebase 16. An automatic recorder controller 22 is mounted on the headportion 20 and is connected to control the horizontal and verticalmovements of the table 18 in accordance with a preselected temperaturesequence as explained later.

In accordance with the invention, a lower press member 25 in the form ofa rectangular plate is mounted on the upper surface of the table I8. Thepress member 25 includes a base portion 26 (FIG. 6) having a pair ofparallel spaced slots 26 (FIG. 5) which divide the base portion 26 intoa pair of end sections 29 on opposite sides of a center section 30. Astrip 32 of insulation material, such as a strip ofpolytetrafluoroethylene, is mounted within each of the slots 28 as shownin FIG. 10.

The base section 26 of the press plate 25 is provided with alongitudinal flat edge surface 34 (FIG. 6) to which an edge portion 35is secured by a series of screws 36. A longitudinally extending slot 38of rectangular cross section is formed within the edge section 35 havingthe surface 34 as one side, and a corresponding parallel spaced slot 39formed within the base portion 26. A U-shaped frame 45 (FIG. 3) includesa pair of parallel spaced legs 46 which are slidably mounted within thecorresponding slots 35 and 39 within the press member 25. The legs 46are rigidly connected by a bar 48 and each leg is provided with alongitudinally extending slot 49.

A threaded stud 55 FIGS. 3 and 6) extends through the base portion 26and has an inner end portion 56 which is received within thecorresponding slot 49. Another threaded stud 55 extends through the edgeportion 55 of the lower press member 25 and has an inner portion 56received within the slot 49 of the other leg 46 so that the studs 55cooperate to retain the frame 45 on the lower press member 25. A locknut 58 is mounted on each of the studs 55 for securing the studs rigidlyto the lower press member after it is properly adjusted.

A vertically extending pin 60 (FIG. 3) is mounted on the end portion ofeach leg 46 of the frame 45, and a pair of L- shaped stop members 62 aremounted on one end of the press member by screws 63 and extend into theslots 38 and 39 for engaging the end surfaces of the legs 46 and therebylimit the movement of the frame to the right (FIG. 3). The studs limitthe movement of the frame to the left.

Referring to FIGS. 5 and 10, the center section 30 of the lower pressmember 25 has a flat top surface which is spaced slightly below thecorresponding top surface 66 of the adjacent end sections 29 and forms arecess between the insulation strips 32 for receiving two original ormaster plates P and P each having an engraved face. Each master plate issecured to the center section 30 by a pair of screws 68 and the engravedface of each master plate projects slightly above the top surfaces 66 ofthe end sections 29 by approximately .010 inch.

Referring to FIG. 9, each end section 29 and the center section 30 ofthe press member 25 is provided with a series of parallel spacedpassageways 70 which extend laterally between the slots 38 and 39 andare connected on opposite ends by longitudinally extending passageways72. A series of plugs 74 are press-fitted into the passageways 72 and aseries of threaded plugs 76 close the corresponding ends of thepassageways 70 to form a serpentinelike flow path between an inlet port77 and an outlet port 78. Referring to FIG. 6, the inlet and outletports are formed within the press member 25 under the rail 39 and areconnected to the adjacent passageways 72 by short vertically extendingpassageways 80 (FIG. 6) which are closed at the bottom of the pressmember by corresponding plugs 82.

Referring to FIG. 7, the inlet ports 77 of the end sections 29 of thepress member 25 are connected by lines to a water supply line 86 througha flexible line 87 and including a manual shutoff valve 88. Thedischarge port 78 of each end section 29 are connected by lines 90 and91 through a flexible line 92 to a drain line 94 having a check valve95. The inlet port 77 of the center section 30 of the press member 25 isconnected by a line 97 and a flexible line 98 to a steam supply line 100in which is mounted solenoid control valve 102, a manual shutoff valve103, a pressure gauge 104 and a pressure regulator 105. The lines 97 and98 are also connected to a water supply line 108 having a check valve109, a solenoid controlled valve 110 and a manual shutoff valve 111. Thewater supply line 108 connects with the water supply'line 86.

The outlet port 78 of the center section 30 is connected by a line andflexible line 116 to a drain line 118 which is normally connected to thedrain line 94 through a three-way solenoid controlled valve 120. Acondensate line 122 connects the valve to the drain line 94 on theopposite side of the check valve 95 and is provided with a strainer 124,a steam trap 125 and a check valve 126. The solenoid controlled valves102, 110 and 120 are actuated by the recorder controller 22 which iscontrolled by a thermocouple mounted within the center section 30 of thepress member 25. Leads 132 connect the thermocouple 130 to thecontroller 135.

Referring to FIGS. 2, 4 and 6, a stationary upper press member in theform of a rectangular plate, is mounted within the head 20 of the press15 and is disposed directly above the center section 30 of the lowerpress member 25 when the table 18 is retracted. The upper press member140 includes end mounting flanges 141 and may be provided with internalpassageways 142 (FIG. 6) corresponding to the passageways 70 and 72within the center section 30 of the lower press member 25, for heatingand cooling the upper press member simultaneously with the centersection 30. Experimentation has shown, however, that the additionalheating and cooling of the upper press member 140 is not necessary toobtain satisfactory performance of the apparatus.

A resilient rectangular blanket 145, preferably of a rubberfabricmaterial and having a uniform thickness, extends over the bottom flatsurface 146 of the upper press member 140. The blanket has opposite endportions which extend into corresponding grooves 148 formed within thepreset member and the end portions are secured by corresponding clampingbars 149.

To produce a mat with the apparatus constructed in accordance with theinvention, a sheet 155 FIGS. 2 and 3) of thermoplastic material such as'vinyl and having a pair of prepunched holes 156, is mounted on the frame45 so that the pins 60 project into the holes 156. The valve 88 isopened so that cooling water is continuously circulated through the endsections 29 of the lower press member 25 thereby cooling the topsurfaces 66 of the end sections 29.

The recorder controller 22 is manually actuated to initiate apredetermined cycle which begins with retracting the table 18 under thehead 20. The table 18 and lower press member 25 are then moved upwardlywith relatively light pressure so that the sheet 155 of vinyl lightlycontacts the blanket on the upper press member 140 and is thereby heldin light contact with the engraved faces of the master plates P and PWhen the table is retracted, it actuates a switch which opens thesolenoid'controlled valve 102 and closes the valve 110. When thecontroller 22 senses a temperature rise through the thermocouple 130,valve 120 is actuated to connect return line 118 to the condensate line122 so that steam is circulated through the center section 30 of thelower press member 25 which raises the temperature of the master platesP and I" and the overlying portion of the vinyl sheet 155.

When the center section 30 of the lower press member 25 reaches apredetermined curing temperature, which can be adjustably set, thethermocouple 130 signals the controller 22 which energizes the hydrauliccylinder within the press 15 so that it applies full force upwardly onthe table 18. As a result, the engraving faces of the plates P and P arepressed into the vinyl sheet thereby producing corresponding impressionsI, and I within the sheet as illustrated in FIG. 8 on the righthandportion of the sheet 155.

Substantially simultaneously with the application of full pressure onthe lower press member 25 against the upper press member 140, whichproduces a force on the order of 12 tons, the recorder controller 22closes the valve 102, opens the valve 110 and actuates the valve 120 sothat the line 118 is connected directly to the drain line 94. Thus thetemperature of the center section 30 of the lower press member 25 andthe master plates P and P and the vinyl sheet 155 begins to drop. Whenthe temperature of the center section 30 reaches a predetermined lowerlimit, which can be adjustably set, the thermocouple 130 signals thecontroller 22 which actuates the hydraulic cylinder in the press 15 tolower the table 18 and thereby release the pressure between the upperand lower press member, after which the table 18 automatically returnsto its extended position as shown in FIG. 1.

After one set of impressions I and I are formed within the vinyl sheet155 from the master plates P and P the frame 45 and sheet 155 are movedto the right (FIG. 3) until the ends of the legs 46 engage the stopmembers 62. In this position, the right-hand portion of the vinyl sheet155 which has the impressions I and I is positioned adjacent the topsurface 66 of the right end section 29 of the lower press member 25 andthe left end portion of the sheet is positioned over the engraved facesof the master plates P, and P The recorder controller 22 is actuatedagain so that the operational steps of the cycle described in thepreceding paragraphs are repeated automatically which results inproducing a sheet 155 having another set of impressions I and I (FIG. 8)in precise registration to the corresponding first set of impressions Iand I The sheet 155 is then cut or sheared along the line to produce twomats each having a pair of identical impressions in preciseregistration. Each mat is then used to produce a two-0n letterpressplate using the same procedure as mentioned above for producing a platewith a single impression.

From the drawings and the above description, it can be seen that theapparatus and method for producing a mat in accordance with theinvention provides several desirable features and advantages. Forexample, by connecting the center section 30 of the lower press member25 to corresponding water and steam supply and discharge lines havingautomatically controlled valves, the center section 30 may be heatedwithin the press for preheating the master plates and the vinyl sheetand then cooled while full pressure is applied between the press membersto produce a mat without requiring the transfer of the master plate froma preheating clamshell to a molding press. As a result, the timerequired for forming an impression within the vinyl sheet issignificantly reduced. In addition, the cooling under pressure preventsshrinkage of the image.

The slidable frame 45 and its cooperating cooperation with the threesection lower press member also provide important features of theinvention. That is, the frame 45 provides for shifting the vinyl sheet155 by a precise predetermined distance after one impression is made sothat a second identical impression can be formed within the sheet inprecise registration with the first impression. The continuous coolingof the end sections 29 is effective to prevent the adjacent portion ofthe overlying half portion of the vinyl sheet from being heated when theother half portion is being heated and pressed against the face of themaster plate, and thereby prevents warping and distortion of theadjacent portion of the vinyl sheet.

Instead of producing two two-on mats as shown in FIG. 8, it can be seenthat the master plates P and P could be formed integrally or rigidlyconnected with the corresponding engraved faces in precise registrationso that a four-on mat could be produced with all of the impressions inprecise registration. A typical application for a four-on mat would befor producing a letterpress plate having two-on double page impressions.By providing an automatic control system as shown in FIG. 7 forcirculating steam or water through the center section of the lower pressmember 25, and controlling the operation of the system by a thermocouplewhich senses the temperature of the center section 30, each mat receivesthe same treatment so that the impressions on each mat of a color setwill have precisely the same registration and thereby substantiallyreduces the time for mounting and positioning the plates on the platecylinders of the letterpress.

While the form of apparatus and process herein described constitutes apreferred embodiment of the invention, it is to be understood that theinvention is not limited to this precise apparatus and process, and thatchanges may be made therein without departing from the scope of theinvention.

lclaim:

11. Apparatus for use in making a multiple impression plate for aletterpress, comprising a first press member having a surface forreceiving a master plate with a predetermined face, a frame memberslidably mounted on said first press member and having means forengaging a sheet of thermoplastic material, stop means effecting precisepredetermined movement of said frame member relative to said first pressmember to provide for selective shifting of said sheet between first andsecond positions to locate first and second portions of said sheet oversaid face of said master plate, means for preheating each of the sheetportions disposed over said face, a second press member spaced from saidfirst press member, press means providing relative linear movementbetween said first and second press members for pressing each portion ofthe sheet against said face to mold an impression within each portion ofthe sheet, and means for cooling each portion of the sheet to form a mathaving two identical impressions each conforming to said face of saidmaster plate and arranged in precise predetermined registration.

2. Apparatus as defined in claim 1 including means defining a fluidpassageway within said first press member in close spaced relation tosaid surface, automatic control means for alternately circulatingheating and cooling fluid through said passageway to effect said heatingand cooling of each portion of the sheet, and means for sensing thetemperature of said first press member to provide for switching betweenheating and cooling fluid in response to predetermined temperature ofsaid master plate said sheet.

3. Apparatus as defined in claim 1 wherein said frame includes parallelspaced legs, means defining parallel spaced slots within said firstpress member and receiving sai legs, and a pin projecting upwardly fromeach said leg for receiving a corresponding hole formed within saidsheet to locate said sheet in fixed relation to said frame.

4. Apparatus as defined in claim 1 wherein said first press memberincludes a center section between opposite end sections, said centersection having said surface for receiving said master plate andincluding means defining a fluid passageway, means defining a separatefluid passageway within each said end section of said press member, saidframe member being effective to position selectively each portion of thesheet over said center section and over one of said end sections, meansfor selectively circulating heating and cooling fluid through saidpassageway within said center section, and means for circulating coolingfluid through said passageway within each said end section.

5. Apparatus as defined in claim 4 wherein said passageway within eachsaid section has a serpentinelike configuration to direct fluid in sucha manner to provide uniform heating and cooling of the correspondingsaid section of said first press member.

6. Apparatus as defined in claim 4 including means defining a slotwithin said first press member between adjacent said sections tominimize heat transfer between said sections.

1. Apparatus for use in making a multiple impression plate for aletterpress, comprising a first press member having a surface forreceiving a master plate with a predetermined face, a frame memberslidably mounted on said first press member and having means forengaging a sheet of thermoplastic material, stop means effecting precisepredetermined movement of said frame member relative to said first pressmember to provide for selective shifting of said sheet between first andsecond positions to locate first and second portions of said sheet oversaid face of said master plate, means for preheating each of the sheetportions disposed over said face, a second press member spaced from saidfirst press member, press means providing relative linear movementbetween said first and second press members for pressing each portion ofthe sheet against said face to mold an impression within each portion ofthe sheet, and means for cooling each portion of the sheet to form a mathaving two identical impressions each conforming to said face of saidmaster plate and arranged in precise predetermined registration. 2.Apparatus as defined in claim 1 including means defining a fluidpassageway within said first press member in close spaced relation tosaid surface, automatic control means for alternately circulatingheating and cooling fluid through said passageway to effect said heatingand cooling of each portion of the sheet, and means for sensing thetemperature of said first press member to provide for switching betweenheating and cooling fluid in response to predetermined temperature ofsaid master plate said sheet.
 3. Apparatus as defined in claim 1 whereinsaid frame includes parallel spaced legs, means defining parallel spacedslots within said first press member and receiving said legs, and a pinprojecting upwardly from each said leg for receiving a correspondinghole formed within said sheet to locate said sheet in fixed relation tosaid frame.
 4. Apparatus as defined in claim 1 wherein said first pressmember includes a center section between opposite end sections, saidcenter section having said surface for receiving said master plate andincluding means defining a fluid passageway, means defining a separatefluid passageway within each said end section of said press member, saidframe member being effective to position selectively each portion of thesheet over said center section and over one of said end sections, meansfor selectively circulating heating and cooling fluid through saidpassageway within said center section, and means for circulating coolingfluid through said passageway within each said end section.
 5. ApparatuSas defined in claim 4 wherein said passageway within each said sectionhas a serpentinelike configuration to direct fluid in such a manner toprovide uniform heating and cooling of the corresponding said section ofsaid first press member.
 6. Apparatus as defined in claim 4 includingmeans defining a slot within said first press member between adjacentsaid sections to minimize heat transfer between said sections.